What's the right way to prepare graysclale images to print in photoshop?

[Jul B]

Hello!
I'm preparing a book to be printed in 2 colors in Indesign, and I have black & white photos throughout the book. I wanted to ask how I can properly prepare the images in Photoshop for printing. Should I convert images to Grayscale, or Duotone? I want to keep them black and white.

Is there an expert in this area around here?

Thank you so much!

[Derek Cross]

Before answering do you want the images printed in black and white (grayscale) with say the text in colour or do you want the images printed in two colours (duotone) and if the latter is the second colour to be a special spot colour or from CMYK?

[Jul B]

Hi Derek, thank you for your time!

I want the images to be black and white. The text will be black with some titles in blue.

[Stephen Marsh]

Should I convert images to Grayscale, or Duotone? I want to keep them black and white.

By @Jul B

Keep them as Grayscale, even though InDesign doesn't have Grayscale mode, it will use the K channel of the CMYK profile for the document or application for the TRC/Dot Gain display.

Your choice of grayscale profile to convert to if currently in RGB would be dependent on your expected printing conditions. This could be the K channel of ISO Coated v2/Fogra 39 or GRACoL 2006 or perhaps an ICC profile for uncoated paper etc. Avoid using generic Dot Gain profiles and don't use gamma based profiles.

[Jul B]

Hi Stephen, thank you for your reply!
Which profile option would you recommend I use? I noticed it was automatically set to "Dot Gain 20%", and the images appeared much darker when placed in InDesign. To maintain the tone I want, should I select "Don't color manage this document"?

[D Fosse]

Here's how you do it:

Under working gray, click "load gray". Then navigate to the appropriate CMYK profile that you will use for printing.

It will look like this in Color Settings:

When you've done this, "Black Ink <CMYK", will appear as a regular option in Convert to Profile and Assign Profile. If you already have grayscale documents, you can now convert them to this, or you can create new documents.

These will print on the black plate only, and match what you see on screen in Photoshop.

[Stephen Marsh]

@D Fosse 

Thanks for posting for clarity... In my example I showed your method on the left and on the right I was using a special custom ICC profile for my grayscale with the same TRC as the CMYK profile. This may have been confusing. :]

The way that you indicate in more detail is useful if one doesn't have a dedicated grayscale profile for the same print condition.

[D Fosse]

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@Stephen Marsh wrote:

In my example I showed your method on the left

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So you did, Stephen, I just wanted to show that you can easily apply the CMYK K channel directly to grayscale documents, thus simplifying the process considerably.

The important thing to keep in mind is that InDesign will natively treat grayscale documents as 0-0-0-K.  Using this method, it will be appropriately treated throughout.

[Jul B]

Thank you D Fosse 🙂

[Stephen Marsh]

Hi Stephen, thank you for your reply!
Which profile option would you recommend I use?

In both Photoshop and InDesign you should use the correct ICC profile that describes the intended print condition! Perhaps your print service provider can recommend what target condition to aim for.

Is this coated paper for sheet-fed offset printing? If so, if you're in the U.S.A., then a GRACoL ICC profile may be a good choice. If anywhere else, you may be better off using a Fogra39/ISO Coated v2 profile.

If uncoated paper, then a different profile would be used.

I noticed it was automatically set to "Dot Gain 20%", and the images appeared much darker when placed in InDesign.

By @Jul B

As I mentioned earlier, InDesign doesn't have a Grayscale working space and uses the K of the CMYK profile assigned to the document or colour settings.

The legacy default Dot Gain 20% from Photoshop doesn't match current TVI found in common printing conditions.

[Jul B]

Thank you! 🙂

[Derek Cross]

In addition to the excellent suggestions offered, have you also discussed this matter with your printer – such as what kind of PDF do they want, how much bleed, do they want crop marks or not and do you want a self-cover or a separate cover document?

[Jul B]

Thank you Derek 🙂

[NB, colourmanagement]

@Jul B @D Fosse writes:"Under working gray, click "load gray". Then navigate to the appropriate CMYK profile that you will use for printing."

'appropriate CMYK'  is a very important phrase here.

@Stephen Marsh writes: "you should use the correct ICC profile that describes the intended print condition! Perhaps your print service provider can recommend what target condition to aim for."

so,  the: "appropriate" profile that @D Fosse mentioned is "the correct ICC profile that describes the intended print condition" as described by @Stephen Marsh

Its all about the print condition. 

That ICC profile will tell Photoshop what dot gain* to expect, i.e., what values to use to ensure your file values are printed with an appearance that reflects those intended values, 20% = 10%, 30% = 30% etc. If the press dotgain is not correctly accounted for then your greyscale will not print as expected. 

*(dot gain is tonal increase due to the spreading of ink on paper making the printed material appear darker than intended)

I hope this helps neil barstow, colourmanagement net - adobe forum volunteer - co-author: 'getting colour right' google me "neil barstow colourmanagement" for lots of free articles on colour management Help others by clicking "Correct Answer" if the question is answered. Found the answer elsewhere? Share it here. "Upvote" is for useful posts.